EP2713477A1 - Method for operating an electric circuit for a wind farm - Google Patents

Abstract

The method involves operating an inner park network (16) of an electric circuit (10) with an operating voltage in a normal operation. Electrical wind energy system generators (13), which are driven by wind energy systems (11), are coupled with the network in the normal operation. The network is operated with another operating voltage in an operating mode different from the normal operation, where the latter operating voltage is smaller than the former operating voltage. The generators are not coupled with the network and/or the network is separated from a power grid in the operating mode. An independent claim is also included for an electric circuit.

Description

The invention relates to a method for operating an electrical circuit for a wind farm, wherein the electrical circuit has a first network, wherein the first network in a normal operation, in which at least one generator driven by a wind turbine generator is coupled to the first network, with a first Operating voltage is operated.

The invention further relates to an electrical circuit according to the preamble of patent claim 8.

In a wind farm, a plurality of wind turbines (WEA) are connected via respective generators (WEA generators) to a first network, which is also referred to as an inner-park network, connected. Furthermore, usually at least one of a diesel generator driven electric generator (diesel generator) is provided, which is provided to cover the so-called own use of the wind farm, if the wind turbines generate substantially no electrical energy and otherwise no energy supply to the wind farm, for example, from a land-based power grid more is available. The said internal requirement is the electrical energy required to operate the wind farm.

In particular, in a net replacement operation, in which the wind farms of the wind farm are fed by the diesel generator, and in which there is no connection to the terrestrial power grid, an exact compensation of the charging power required for the operation of the internal parking network, which results from the reactive power demand of the inner parking network, is very difficult because the lengths of the cables belonging to the internal network ("cable laying lengths") and the electrical parameters of these cables are not known exactly. In addition, the electrical parameters such as e.g. a capacity coating of the cable production-related variations, which further complicates a prediction of the charging power for an existing inner-car network. In addition, the diesel generators provided to cover their own needs have limited ability to deliver the reactive power required to provide the charging power. Thus, in the conventional systems, a reliable domestic power supply is not always guaranteed.

Accordingly, it is an object of the present invention to ensure a reliable domestic power supply of a wind farm even if no energy supply to the wind farm, for example, from a land-based energy supply network is no longer available.

This object is achieved in the method of the aforementioned type according to the invention that the first network (Innerparknetz) is operated in a different mode from the normal operation with a second operating voltage, wherein the second operating voltage is smaller than the first operating voltage.

According to the invention, it has been recognized that, in the operation of the inner-park network with a lower operating voltage than the normal operating mode, a reactive power demand of the inner-park network is lower, which is due to the lower charging power of, inter alia, the cables of the inner-park network. It is therefore proposed to operate the inner-park network at a lower operating voltage during the second operating mode, which is different from normal operation, in order to reduce its charging power. This has the further advantage that also the variance of the charging power, which results from the insufficient knowledge of the exact cable laying lengths and cable parameters, is reduced. Due to the lower reactive power requirement on the one hand, and the concomitant likewise reduced variance of the reactive power requirement on the other hand, a more reliable supply of the internal parking network in the second operating mode is made possible. This applies in particular to operating scenarios in which the inner-park network is not coupled to another network, such as a land-based energy supply network, which can usually contribute to covering the unpredictable reactive power demand of the inner-park network. Advantageously, the method according to the invention enables reliable operation while providing the charging power for the inner-park network even if, for example, only one diesel generator is available to maintain the operation of the inner-park network, for example to ensure the self-supply of the wind farm.

In an advantageous embodiment, it is provided that in the second operating mode a) at least one generator driven by a wind energy plant is not coupled to the first network and / or b) the first network is separated from a power supply network. In particular, the second operating mode, in which the first network (internal parking network) is operated according to the invention with a lower operating voltage than the normal operating mode, can be a network replacement operation. In the normal operating mode, the inner-park network is coupled, for example, to a land-based energy supply network, so that any required reactive power for the inner-park network can be obtained from the land-based energy supply network. Alternatively or additionally, in the normal operating mode, one or more generators driven by a corresponding wind energy plant may also be coupled to the first network.

In an advantageous embodiment, it is provided that the first operating voltage is about 33 kV (kilovolts) or more, and that the second operating voltage is between about 0.4 kV and about 6 kV. The second operating voltage may also be about 10 kV or more. The proposed for normal operation of the first network voltage of about 33 kV, for example, corresponds to the secondary voltage of transformers associated with the WEA generators and allows a relatively low-loss electrical energy transmission over the first network, for example, the electrical energy obtained by the WEA generators to be forwarded to a supply network. The proposed for the second mode, in particular the net replacement operation, smaller preferred operating voltage between preferably about 0.4 kV and about 6 kV advantageously requires compared to the first operating voltage of about 33 kV significantly reduced charging power of the first network, since the charging power is proportional to the square the operating voltage is. In addition to an absolutely significantly reduced charging power of the internal parking network results from the reduced second operating voltage and a clear reduced variance of the charging power for an existing internal parking network, which, as already described, is due to not exactly known cable lengths and cable parameters of the cables used for the internal parking network. This advantageously makes it possible to reliably provide the charging power in the second operating mode with a diesel generator and / or other energy supply means local to the wind farm, in particular even if the charging power required for the operation of the first network does not consist at least partially of a (land-based) energy supply network or of a WEA generator can be obtained.

In a further advantageous embodiment, it is provided that in the second operating mode, at least one generator providing the second operating voltage is connected to the first network so that the power required for its own power is fed directly from the generator into the first network, ie the inner-parking network can. The generator may preferably be a diesel generator. Other electric generators or batteries with inverter or the like are also conceivable. For example, the generator may provide an AC voltage of about 0.4 kV or about 6 kV or other voltage levels for operation of the inner-park network. The generator can be advantageously integrated in a wind turbine of the wind farm or on a wind farm associated platform of an offshore substation, etc.

In a further advantageous embodiment, it is provided that the generator is connected via a transformer to the first network, so that a voltage provided by the generator can be transformed to another voltage level in order to feed or operate the first network. For example, the generator may have an output voltage of 0.4 kV, which is transformed by means of its associated transformer to a voltage level of, for example, 2kV or 6kV, to thereby feed the first network.

In a further advantageous embodiment, it is provided that in the second operating mode, at least one wind energy plant is supplied with electrical energy via the first network by the second operating voltage to cover its own requirements. Due to the inventively reduced operating voltage during the second mode advantageously results in a simple and efficient operation of the first network even when the electrical energy is provided for self-supply and for the operation of the first network of a generator.

In a further advantageous embodiment, it is provided that at least one consumer contributing to an electrical intrinsic demand of a wind energy plant is connected in the second operating mode either directly or via an in-house transformer to the first grid.

Another solution to the object of the present invention is given by an electrical circuit according to claim 8.

Other features, applications and advantages of the invention will become apparent from the following description of embodiments of the invention, which are illustrated in the figures of the drawing. All described or illustrated features, alone or in any combination form the subject matter of the invention, regardless of their summary in the claims or their dependency and regardless of their formulation or representation in the description or in the figures.

Figur 1

schematisch ein Blockschaltbild eines Ausführungsbeispiels einer erfindungsgemäßen elektrischen Schaltung,

Figur 2a bis 2d

jeweils weitere Ausführungsformen der erfindungsgemäßen elektrischen Schaltung,

Figur 3

schematisch ein Blockschaltbild eines weiteren Ausführungsbeispiels einer erfindungsgemäßen elektrischen Schaltung, und

Figur 4

ein vereinfachtes Flussdiagramm einer Ausführungsform des erfindungsgemäßen Verfahrens.

In the drawing shows:

FIG. 1

1 is a schematic block diagram of an embodiment of an electrical circuit according to the invention;

FIGS. 2a to 2d

in each case further embodiments of the electrical circuit according to the invention,

FIG. 3

schematically a block diagram of another embodiment of an electrical circuit according to the invention, and

FIG. 4

a simplified flow diagram of an embodiment of the method according to the invention.

In the FIG. 1 is an electrical circuit 10 of a so-called offshore wind farm shown, so located at sea, spatial accumulation of a plurality of wind turbines (wind turbine = wind turbine).

In the FIG. 1 For example, two wind turbines 11 are shown, each of which is intended to convert the kinetic energy of the wind into electrical energy. For this purpose, each of the wind turbines 11, which are usually constructed on sea-bound platforms, has in each case one wind wheel 12, which is mechanically coupled to an electric wind turbine generator 13 and drives it.

The electrical energy generated by the WEA generators 13 is fed via a respective WEA transformer 14 and via a respective WEA switch 15 in a first busbar 16 a of a first network 16. By way of example, the first network 16 may be a medium-voltage three-phase supply network of 33 kV, which is also referred to as an inner-park network, because it connects the wind energy installations 11 of the wind farm to one another. The inner-park network 16 is provided essentially for all lake-bound facilities of the wind farm and is therefore located essentially at sea.

The first busbar 16a of the internal parking network is connected via a busbar switch 17 to a second busbar 16b of the internal parking network 16.

The second busbar 16b of the internal parking network 16 is connected via a main switch 18 and a main transformer 19 to a transmission network 20, for example with a high voltage three-phase system of 155 kV. The transmission network 20 is essentially intended to transmit the electrical energy generated within the wind farm to the mainland. As part of the transmission network 20 may also be alternatively or additionally a DC voltage transmission available. The transmission network 20 is also referred to as a second network.

The transmission network 20 is connected to a non-illustrated land network, which is for example, located on the mainland energy supply network of a power company, are supplied to the industrial equipment and households with electrical energy.

On a platform of one of the wind turbines 11 or on another lake-bound platform of the wind farm, an internal combustion engine 22 is present, for example a diesel engine. It is understood that instead of the internal combustion engine 22, any other, non-electric unit may be present, which is adapted to set a generator in a rotational movement.

Via a mechanical coupling, the internal combustion engine 22 drives a generator 23, which is connected via a transformer 24 and a switch 25 to the second busbar 16b of the internal parking network 16. It is understood that a plurality of internal combustion engines 22 and / or a plurality of generators 23 and / or a plurality of transformers 24 and / or a plurality of switches 25 may be present, which may be connected in parallel. As an alternative to the generator 22, it is also possible to provide a battery system (not shown) or a fuel cell or the like, to which an inverter for generating an alternating voltage is assigned.

The individual platforms of the wind turbines 11 as well as the possibly existing, other platforms of the wind farm must be supplied for their operation with electrical energy. This is also called so-called own use of the wind farm. This internal requirement is usually satisfied in a normal operation by the inner park network 16 with the aid of the wind energy systems 11 supplying electrical energy.

However, the intrinsic demand must essentially always be ensured, ie even if, for example, during a storm, the wind turbines 11 are turned off and the WEA generators 13 so that essentially no electrical energy supply to the first network 16 more. In this case, in the electrical circuit 10 of the intrinsic demand of the wind farm is satisfied that the first network 16 is connected via the transmission network 20 to the land network and thus the first network 16 is supplied by the land network with electrical energy. Thus, in the electric circuit 10, even when the wind power plants 11 are switched off, the intrinsic demand of the wind farm can be ensured essentially always via the transmission network 20 from the land network.

Only in the case of an interruption of the connection from the first network 16 (inner park network) to the land network, so for example in the event of an interruption of the transmission network 20, the intrinsic demand of the wind farm is not guaranteed. In this case, however, the engine 22 is provided with the generator 23 and the transformer 24.

While in a normal mode in which the first network 16 may receive electrical power from either the wind turbines 11 and / or the transmission network 20 (in the case of decommissioning of the wind turbines 11), the first network 16 is connected to a first operating voltage of e.g. about 33 kV is operated, is provided according to the invention that in a deviating from the normal operation second mode, the first network 16 is operated with a second operating voltage which is smaller than the first operating voltage of about 33 kV. This on the one hand ensures that a reactive power requirement for the operation of the first network 16 (so-called charging power) compared to the normal operation with e.g. 33 kV drops. Furthermore, the variance of the reactive power demand also decreases accordingly, so that the first network 16 can also be operated reliably by means of the generator 23, in particular in order to still cover the internal demand of the wind farm.

The second mode thereby differs from the first mode, i. Normal operation that in the second mode at least one of a wind turbine 11 powered generator 13, but preferably all generators 13 are not coupled to the first network 16 and / or the first network 16 is disconnected from a power grid. This is the case, for example, when the wind turbines 11 are at least temporarily shut down, e.g. due to a storm, and at the same time there is no connection between the first network 16 and the land network, for example due to an interruption of the transmission network 20.

If, therefore, it is found when wind turbines 11 are switched off that no electrical energy can be transmitted from the land network to the inner park network 16 via the transmission network 20, the intrinsic demand of the wind farm is covered in accordance with the procedure described below.

According to the invention, the inner parking network 16 is operated in the second operating mode with a lower operating voltage than the normal operating mode. The second operating voltage is for example between about 0.4 kV and about 6 kV. This advantageously results in a significantly reduced reactive power requirement (charging power) compared to normal operation for the operation of the inner parking network 16, so that the generator 22 in the second operating mode advantageously has to provide much less reactive power for the operation of the inner parking network 16 than for normal operation at e.g. 33 kV is required. Furthermore, due to not exactly known cable laying lengths and cable parameters of the internal parking network 16 conditional variance of reactive power demand is also reduced, so that an exact compensation of the charging power of the internal parking network 16 by the generator 23 is easier than at the voltage level of 33 kV in normal operation.

FIG. 4 shows a simplified flowchart of an embodiment of the method according to the invention. In a first step 100, the inner-park network 16 (FIG. FIG. 1 ) in a first mode, the normal operation operated. In this case, the switches 15, 17, 18 ( FIG. 1 ), so that the inner park network 16 of the wind turbines 11 and possibly the transmission network 20 with electrical energy and in particular with reactive power, namely as charging power for the inner park network 16, can be supplied.

A similar operating scenario, in which the switches 17, 18 are closed, but the switches 15 are opened, is also considered in the present case as normal operation, because the inner-park network 16 can still be supplied by the transmission network 20 with the charging power. Similarly, a configuration in which at least one switch 15 is closed, but the switch 18 is open, be considered as normal operation, because then the charging power for the inner-park network 16, although not obtainable from the transmission network 20, However, can be supplied by the switch 15 associated wind turbine 11.

In contrast, results in step 110 FIG. 4 a second mode, which is different from the normal operation of the step 100, then, when the switches 15 and 18 are open, the inner-park network 16 can therefore be supplied neither by a wind turbine 11 nor by the transmission network 20 with the charging power necessary for its operation.

In this second mode of operation, the switch 25 is advantageously closed so that the diesel generator 23 can supply the internal parking network 16 via the transformer 24 with an operating voltage. According to the invention, this operating voltage for the second mode of operation is less than the operating voltage of approximately 33 kV in normal operation, so that the diesel generator 23 has to provide less charging power for the inner-park network 16 than is required in normal operation.

To be able to cover the internal requirements of the wind turbines, the switch 17 is closed in addition to the switch 25, so that both sections 16a, 16b of the internal parking network 16 are interconnected and operable with the operating voltage for the second mode.

FIG. 2a shows an embodiment of the invention, in which a WEA generator 13 of a wind turbine of the wind farm or its associated WEA transformer 14 are decoupled by means of the switch 15 of the inner park network 16 and its first portion 16a. In order nevertheless to be able to cover the own demand of the considered wind power plant, an in-house transformer transformer 141 of the wind energy plant can be connected to the inner-park grid 16 by means of the switch 152. Block 158 off FIG. 2a symbolizes the self-consumption of the wind turbine representing consumers or a corresponding self-consumption subnet.

In normal operation 100 ( FIG. 4 ), the switches 15, 151 are closed, and the switch 152 is open. As a result, the WEA generator 13 can feed electrical power via the WEA transformer 14 and the switch 15 into the inner-park network 16. The domestic power transformer 141 is powered by the switch 151 directly from the WEA generator 13 with energy. In normal operation, the internal parking network 16 is operated, for example, with a first operating voltage of approximately 33 kV.

In the second mode 110 ( FIG. 4 ), the switches 15, 151 are open, and the switch 152 is closed. Now, the domestic power transformer 141 draws electrical energy directly from the internal parking network 16, which is fed for this purpose by the diesel generator 23 as already described. In the second operating mode, the inner-park network 16 is operated, for example, with a second operating voltage of, for example, approximately 2 kV, which corresponds, for example, to the output voltage of the WTG generator 13 in normal operation. Thereby, the in-house power transformer 141 can be selectively connected to the WEA generator 13 or the inner-car network 16. The domestic power transformer 141 transforms the voltage level of the internal parking network 16 from approximately 2 kV, for example, to 0.4 kV for the supply of the domestic consumers 158.

As a result of the operating voltage of the inner-park network 16 being reduced in the second operating mode compared to normal operation, the diesel generator 23 has to provide less charging power for the inner-park network 16, and the variance of the charging power required is also smaller, which increases the possibility of a more precise supply of the inner-park network 16 with the exact charging power and thus gives a more reliable operation.

FIG. 2b shows a further embodiment of the invention. In contrast to FIG. 2a The self-consumption transformer 141a has two different primary winding terminals 141a, 141a " Primary winding terminals 141a ', 141a "is advantageously selected so that in a normal operation, in which the WEA generator 13 provides an output voltage of approximately 2 kV, the in-house transformer transformer 141a can be connected directly to the WEA generator 13 via its primary winding terminal 141a". and that in the second operating mode, in which the inner-park network 16 is operated with a voltage of approximately 6 kV, the in-house transformer transformer 141a can be connected directly to the inner-park network 16 via its primary winding connection 141a '.

In normal operation, therefore, the switches 15, 151 are closed and the switch 152 is open, so that the auxiliary power transformer 141a is supplied on the primary side via its terminal 141a "from the WEA generator 13 with a voltage of about 2 kV and this in a secondary voltage transformed by about 0.4 kV.

In contrast, in the second mode of operation, the switches 15, 151 are open and the switch 152 is closed, so that the auxiliary power transformer 141a is supplied on the primary side via its terminal 141a 'directly from the internal parking network 16 with a voltage of about 6 kV and this into a secondary voltage transformed by about 0.4 kV. In this case, the diesel generator 23 thus provides, with the aid of its transformer 24, an output voltage of approximately 6 kV for operation of the inner-park network 16.

The connection 141a "can advantageously be designed as a tap on the primary winding of the internal power transformer 141a.

Figure 2c shows a further embodiment of the invention. In this variant, the WEA transformer 14 can be coupled to the inner-park network 16 via the switch 15. In addition, the internal power transformer 141a again has two different primary winding terminals 141a ', 141a ", of which, respectively one via the switches 152, 153 with the inner park network 16 is connectable.

The gear ratio with respect to the primary winding terminals 141a ', 141a "is advantageously selected so that the domestic power transformer 141a in a normal operation, in which the internal parking network 16 is operated with a first operating voltage of about 33 kV, the voltage of 33 kV to an output voltage of eg 0th , 4 kV, and that the auxiliary power transformer 141a in the second mode, in which the internal parking network 16 is operated with an operating voltage of about 6 kV, via its primary winding terminal 141a 'directly to the internal parking network 16 is connectable and the voltage of 6 kV to a In normal operation, therefore, the switches 15, 153 are closed and the switch 152 is open, so that the auxiliary power transformer 141a on the primary side via its terminal 141a "from the internal parking network 16 with a voltage of about 33 kV is supplied and transformed into a secondary voltage of about 0.4 kV.

In contrast, in the second mode of operation, the switches 15, 153 are open and the switch 152 is closed, so that the auxiliary power transformer 141a is supplied on the primary side via its terminal 141a 'directly from the internal network 16 with a voltage of about 6 kV and this into a secondary voltage transformed by about 0.4 kV.

Figure 2d shows a further variant of the invention, in which the domestic power supply via the switch 154 can be made directly from the inner park network 16. In this case, the inner-park network 16 in the second operating mode is accordingly to be operated with a suitable voltage of, for example, approximately 0.4 kV. This operating voltage for the inner-park network 16 can in turn be controlled by the diesel generator 23 (FIG. FIG. 1 ) are provided for this purpose, for example, directly, so Bridging the transformer 24 may be designed to be connected to the inner park network 16.

In normal operation, in which the inner-park network 16 according to Figure 2d For example, is operated at 33 kV, the switch 154 is open, and the switch 155 is closed so that the intrinsic demand 158 of the wind turbine can be covered by the auxiliary power transformer 141. For this purpose, the domestic power transformer 141 can be connected on the primary side either to the connection point a1, that is to say to the output of the WTG generator 13, or else to the connection point a2, ie directly to the internal parking network 16. Depending on the use of the connection points a1, a2 and the operating voltages of the components 13, 16 in the normal operation, the transmission ratio of the internal power transformer 141 is suitable to choose.

The above with reference to the FIGS. 2a to 2d described embodiments can also be combined with each other. That is, different wind turbines of the same wind farm can each have different configurations according to the FIGS. 2a to 2d have, in particular, the transmission ratios of any used internal power transformers 141, 141a are to be selected suitable.

FIG. 3 shows a further embodiment of a circuit according to the invention, in which the diesel generator 23 via a transformer 24a with a plurality of secondary winding terminals (unspecified) to which the switches 25a, 25b are associated with the inner park network 16 can be coupled.

For example, in normal operation, the switch 25a is closed, and the switch 25b is open. In this case, the transformer 24a sets the operating voltage of the inner-park network 16 from approximately 33 kV to approximately 0.4 kV to cover the intrinsic demand 158 of, for example, a substation on which Offshore platform (not shown) of the transformer 24a is arranged.

In the second mode of operation, the switch 25a is open and the switch 25b is closed, so that the output voltage of the diesel generator 23 can be transformed to a suitable operating voltage for the internal parking network 16 of about 6 kV.

According to one embodiment, an operating voltage of approximately 6 kV is particularly preferred for the second operating mode of the inner-park network 16 because this voltage is a typical output voltage of common diesel generators 23 or of transformers 24 which are assigned to the diesel generators 23.

In general, the second operating voltage is freely selectable for the operation of the internal parking network 16 and, provided it is less than the first operating voltage of e.g. 33 kV, which is used in normal operation, the advantages of the lower charging power and the lower variance of the charging power described above, so that advantageously can be dispensed with additional actuators for balancing the reactive power, especially in a net replacement operation.

Claims (11)

A method of operating an electrical circuit (10) for a wind farm, the electrical circuit (10) having a first network (16), the first network (16) operating in a normal mode in which at least one wind turbine driven by a wind turbine (11) Generator (13) is coupled to the first network (16), is operated with a first operating voltage, characterized in that the first network (16) is operated in a different operating mode of the second mode with a second operating voltage, wherein the second operating voltage less than the first operating voltage. The method of claim 1, wherein in the second mode a) at least one of a wind turbine (11) driven generator (13) is not coupled to the first network (16) and / or b) the first network (16) separated from a power grid is. The method of any one of the preceding claims, wherein the first operating voltage is about 33 kV or more, and wherein the second operating voltage is between about 0.4 kV and about 6 kV. Method according to one of the preceding claims, wherein in the second operating mode, at least one generator (23) providing the second operating voltage is connected to the first network (16). The method of claim 4, wherein the generator (23) is connected to the first network (16) via a transformer (24). Method according to one of the preceding claims, wherein in the second operating mode at least one wind turbine (11) is supplied via the first network (16) by the second operating voltage with electrical energy to cover its own needs. Method according to one of the preceding claims, wherein at least one consumer (158) contributing to an internal electrical demand of a wind turbine is connected to the first network (16) either directly or via an in-house transformer (141, 141a). Electric circuit (10) for a wind farm, the electric circuit (10) having a first network (16), the first network (16) being operated in a normal mode in which at least one generator (13) driven by a wind turbine (11) is coupled to the first network (16) is operable with a first operating voltage, characterized in that the first network (16) is operable in a second operating mode different from the normal mode with a second operating voltage, wherein the second operating voltage is smaller than that first operating voltage. The electrical circuit (10) of claim 8, wherein the first operating voltage is about 33 kV or more, and wherein the second operating voltage is between about 0.4 kV and about 6 kV. Electrical circuit (10) according to any one of claims 8 to 9, wherein in the second mode, at least one generator (23) providing the second operating voltage is connected to the first network (16). Electrical circuit (10) according to any one of claims 8 to 10, wherein at least one contributing to the electrical intrinsic demand of a wind turbine consumer (158) in the second mode either directly or via an internal power transformer (141, 141 a) with the first network (16) is connectable.

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